The present invention relates to an agricultural tillage system; and more particularly, it relates to a tillage system which is capable of a complete working and plowing of unplowed ground in a single pass.
Perhaps the most commonly used tool for plowing is the conventional moldboard plow. Usually the plow bottom is set at a particular depth of plowing, for example, eight or ten inches, but as deep as twelve or fourteen inches in some cases. These plows are typically mounted to a main beam which is inclined relative to the direction of travel of a tractor so that each moldboard is set to take a swath or strip of ground, cut it, and roll the ground over into a furrow formed by the next forward moldboard. The leading moldboard turns its strip of ground over into a furrow formed on a previous pass of the plow system.
When a moldboard plow is used repeatedly to plow ground at the same depth, a layer of highly compacted soil is formed just beneath that depth. This is called the plow "sole", and it has the disadvantages that, due to its compactness, roots of plants have difficulty in penetrating it, and water has a tendency to drain over the plow sole rather than being absorbed by the soil. Further, a moldboard plow displaces to one side all of the soil that is tilled. Eventually, the ground must be plowed in the opposite direction, and even when this occurs, a deep side ridge normally is left at the end swath.
One advantage of the moldboard plow, not found in devices which work a more shallow depth is that they bring up deep soil and this is believed to be effective in reducing herbicide built up near the surface.
In the case where moldboard plows are used for tilling soil which has not previously been cleared, and may contain some "trash" (that is, crop residue which, in the case of corn, may be bulky and tough), a coulter may be located in front of each moldboard plow to cut through the trash and at least partly through the soil. This reduces accumulation of trash on the leading edge of the moldboard, and it further assists the moldboard in cutting the soil. Coulters are also used in connection with other tillage systems, and they generally are in the form of a relatively flat, circular blade.
Another form of blade that is used in tillage systems is referred to as a "disc", and it takes the shape of a dish or bowl. The edge of the disc blade is used to cut trash, and the concave surface of the blade is used to throw some of the top soil to the side. Typically, a plurality of disc blades are arranged at a relatively close spacing, and they may be mounted on a common shaft which extends at an acute angle relative to a line transverse of the direction of travel of the tractor. When a gang of disc blades is pulled across a field, complete coverage is obtained. That is, all of the soil is tilled, the trash is cut up, mixed with the top soil and some trash is buried. Complete coverage is obtained because the spacing of adjacent discs is typically about forty percent of the diameter of a disc, and the discs are turned slightly to work a path.
In these devices, to reduce the effect of lateral soil displacement due to complete workage, a second line or gang of discs, facing the other direction, may be placed behind a first line. Similarly, a given line or gang may be formed in a chevron shape, symmetrical about the center line of the system. In all such cases, however, the effect of the disc blades is to work all of the soil, rather than selected strips, since the primary purpose of the disc is to cut the trash. If a farmer then treats the disced land with a chisel plow for deeper working of the soil, the chisel plow has the effect of digging up the buried trash, and bringing the trash back to the surface.
Other implements use disc blades, such as listers and bedders, but the function of the disc blades in these implements is to create raised beds for seeds, with lateral troughs for water collection or irrigation.
Another type of implement used to cultivate the soil is referred to as a cultivator sweep, and it takes the form of a V-shaped blade with laterally and rearwardly extending wings which are at the same horizontal level. This type of device breaks the soil and lifts it, but it has the effect of throwing loose soil to the side and compacting the soil beneath it, thereby creating a new plow sole.